The Theory of Necessity
by withered
Summary: Ichigo drowns. Rukia never sleeps.


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The Theory of Necessity

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Ichigo dreams of drowning.

Not necessarily in water, but the general state of it – the air thinning, the suffocation, the panic of being trapped – he gets those feelings sometimes too when he's awake – his hands itch with it, to claw at walls that aren't there, his throat tightening on a scream that no one else will hear. He can be wide awake and know without a doubt that he's drowning.

Because when he takes in his surroundings, all he can make out is the greyscale of dusk drenching his room in shadow, and Rukia sitting in her Shinigami robes beside him, hand aglow over his chest as if to relieve the pressure he'd only imagined in his head.

He pants out a breath like he'd been holding it for too long, and she waits for his racing heart to slow – to calm – before she reaches over to cover his eyes. "Go to sleep, Ichigo," and though she'd said it as an order, the words themselves are soft, soothing. "You had a bad dream."

"Where are you going?" he asks instead, voice rough from disuse.

"Patrolling," she replies, and when his eyes widen in the dark, she soothes once more, "There's no danger, it's just a precaution. The kido on the house will hold so long as you or Karin are here, I'll be right back if they go down for whatever reason."

"That's not -" His head is hazy from sleep, but Rukia is insistent, her fingers moving over his eyelids and down over his lips as if to silence him.

"Rest. You've got school tomorrow."

He'd retort – _so do you _– but she only goes to school to keep an eye on him, provide him with extra support if there are no Hollows to hunt, keep his reitsu hidden beneath the blanket of hers until he learns to hide it himself. No one besides Ichigo and the friends that had gone to Soul Society with him, seem to notice how she flits like a ghost – coming and going from class to class – neither noticed nor missed.

He feels like he's not breathing enough – his eyes burn from the lack of it, his throat straining on the _why_ he knows the answer to but doesn't want to think about.

(She's dead, she's dead and what she needs is different from what he needs.)

But still, he fixates, thinking instead, does Rukia even sleep?

He doesn't think so.

His understanding of her faux body had been that it wasn't a _real one _– that it didn't require things like breathing or eating or rest or sleep.

Right until he'd found her out-conscious beneath a tree in the schoolyard.

His breath had caught, adrenaline shaped like fear coursing through his veins as the possibility of her being attacked sinks in – that she was hurt, that she was –

But the reality – to her scowl – had simply been that she was tired – that she'd waited for him after school because he couldn't be trusted to go home without an escort lest he find himself in trouble. It was prudent to rest when she wasn't needed, and as much as the girls wouldn't turn down the safety of her presence at home, Yuzu is constantly with Dad ever since she'd found out about the whole "my brother is a Soul Reaper" thing, and with Karin's reitsu flaring up, she spent her time between school and Urahara's in a bid to prevent it "leaking like a hose pipe" in Uryuu's words.

Any excuses he'd come up with to hide the fact that he'd been freaked out seeing Rukia lying there had led to the lecture that ended with: "Fool, you never listen, why do I bother even trying to explain it to you?"

Which wasn't helped when he replied: "Was that what that crappy drawing was?"

That she, after allowing her reign of his bed while he tried to study, and been able to read through his emotional constipation enough to recognize he'd just been worried about her, sighed, rolled her eyes and declared him an "idiot" for the first time since that morning. Ichigo figured he was forgiven.

Of course, learning about Rukia's sleeping habits only roused more questions.

Namely: When did she actually sleep?

He'd realized that after coming back from Soul Society – relieving Renji, as she was seemingly less important as an unseated officer – that Rukia didn't sleep when everyone else did, so when did she?

She's the first to wake him – wake them all when the sun comes up.

Ichigo had never been much of an early riser and Shinigami duties do still take up his day on top of his school schedule, and Karin, with pre-Shinigami training in the works and soccer practice on the side, doesn't get enough rest in general. But Yuzu gets nightmares now too, more persistent now that she's refused for her memories to be altered; of things she doesn't know and things she can't stop. She has no reitsu to speak of, and can't sleep a full night with the anxiety of it unless Dad is home.

Rukia takes up the task of getting breakfast sorted out, setting lunches on the table.

(They're grateful, they all are.)

She sits through class, and Ichigo can't tell whether she's awake or not through it unless he wants to bring unnecessary attention to her.

So, he doesn't.

Though he wonders and his lungs burn a little, like's holding his breath to find out that the answer is _yes, she's here even though she should be sleeping, should be resting; she must be tired –_

But now that he has an idea of when she's awake, Ichigo knows what to look out for, how to help. At first, Rukia is only grudgingly appreciative of it: she'll nap when they have lunch, she doesn't need to eat as much as she needs to sleep, and she'll lie behind Ichigo, using their bags as a pillow and his school blazer as a blanket. It's a routine that works for after school too – when Ichigo has class duties or Tatsuki talks him into a sporting event. Rukia will sit on the stands, using his blazer for warmth or extra cushioning, and rest.

And he breathes a little easier for it.

Throughout the day he keeps looking to check on her, glancing over his shoulder to make sure she's alright, keeping a hand on her knee or her shoulder as if to physically remind her that's he's there and won't leave her; constantly drifting out of conversations to make sure they haven't woken her.

If anyone notices, miraculously, no one says anything.

And if he overhears Tatsuki comforting Inoue about how much of Ichigo's attention seems dedicated to Rukia, he pretends not to understand the implications of it from either perspective.

Even if his breath catches.

Rukia, after a great deal of huffing, informs him that she doesn't need his worrying – that it's the complete opposite of why she's here in the first place. He sulks about it for approximately three days before with a huff, she comes into his room while he's studying, makes herself comfortable on his bed, shoots him a look and goes to sleep.

Ichigo already knows that she'll rest so long as he's watching out for her, and her blatantly doing so is enough until the hours don't add up: She can't be getting enough sleep. It starts to feel like drowning again, and between one metaphorical gasp of air and another he tells her, "You know, you can just come back home to sleep instead of going to class, it's not like you need to go to school with me."

"I know that."

"Then why don't you?"

Her eyes narrow for a moment before she looks away. "I don't like it when the house is empty."

_I don't like being alone_, is what he hears, and though he's gotten the impression that her life at Kuchiki Manor was exactly that – alone and empty – and maybe she just didn't like it as a preference – he remembers the stories Renji had told him while he was taking Rukia's place in Karakura: About life in Rukongai, constantly on the run, every day a fight for one more day, one more day, _one more day_ – and Ichigo thinks he understands.

_She feels safer with other people around._

And Ichigo would think that would mean she'd sleep more – she sleeps through lunch, and catnaps while she waits for him at school – but at home, she seems to limit herself to resting only for an hour while he studies.

Mainly because, he's come to realize, Rukia likes to be awake when there are people around too.

Not for the same fear that kept her going in Rukongai, but the same sort of obligation – of duty: She wants to be useful.

The less of a burden she can make of herself the better, despite everything – saving his sisters' lives that fateful night, and saving Ichigo's every day since – Rukia thinks its still her fault, that Ichigo wouldn't be hunting Hollows, that Karin wouldn't be training for the same, that Yuzu wouldn't be afraid if Rukia hadn't come into their lives.

She's wrong, of course.

But that doesn't stop her from waking – from climbing out of bed (his own or the one in the closet she refuses to give up) – and heading out to make sure Karin is getting her kido right, to reassuring Yuzu that she'll be around, to yelling at Ichigo about his shoddy swordsmanship and slower footwork, to making sure she gets to the Hollows before even Ichigo can get the alert on his phone.

Ichigo only realizes that its also because of Rukia's own nightmares that she does it.

She's failed people before, she's gotten them hurt and lost and _killed,_ and she remembers.

Even with her childlike enthusiasm and her annoying arguments with him over Chappy merchandise, fighting over the bathroom and the drill-sergeant training schedule she puts him through, her nightmares keep her going just as much as her guilt does.

He can't comfort her with kido the way she's done for him – for Yuzu, for Karin, even for Dad sometimes – and knowing that waking her would be the exact opposite of what he wants for her – he does the only thing he can: He sits beside her in his bed, runs his fingers through her hair and murmurs nonsense until she stills, until she breathes, until she sleeps.

Hours later, Rukia is so startled at the fact that she's slept so long that she opens her mouth to yell at him (because let's face it, if something goes wrong with her plans, it's probably his doing), and instead asks, "What time is it?"

"Dinner," he replies, clearing his throat and going for casual. "Just finished making it, I was just about to wake you."

Her brows furrow in suspicion, but she doesn't push it, and over the next few weeks, even she seems relieved at the change.

Partly because, she'll say to Karin, that _he _seems to be doing better too.

It doesn't occur to him that she doesn't know why she's sleeping so well until she wakes up from a nap: Ichigo had gone out for a minute to get some water and came back to the sound of her whimpering – and had gotten to her too late to the point where she looked in agony – he has her in his arms in an instant, rubbing her back and murmuring, "I'm here, I'm here, you're okay, everything's going to be okay."

"Ichi…go?"

It doesn't occur to him to be nervous even in the face of her confusion, it doesn't even occur to him to wonder at what his face looks like (scared and relieved and soft and _fond_), or what _they _look like together - cuddled on Ichigo's bed with her in his arms like they do it all the time.

Yuzu, red-cheeked and smiling, apologizes for interrupting, that dinner's ready, but _oh, if they want she can just bring it up and –_

Dinner isn't…awkward, but there's a strangeness to it, and his family is glancing between them both as if waiting for the other shoe to drop.

It doesn't.

Not until they go back upstairs and Rukia's asking, "How long have you been doing that?"

"Doing what?"

She scowls. "You know what."

Still, he feigns confusion, and with a wave of her hand and flush on her cheeks, she poorly elaborates, "The holding and the talking while I was asleep!"

"A few weeks," he says, going for nonchalant, only realizing a moment too late that _she didn't know_, and then they're both standing there with no idea where to look or what to say, until he clears his throat and tells her, "I don't mind, you do it for me."

"That's different."

"How?" he challenges, and when she only continues to frown, he says, "It's not a big deal. You need to rest too and I…I don't mind," and he doesn't – not really.

He minds that she has nightmares, most of which he can't even fathom given how little she talks about her life before meeting him. He minds that she's been hiding it for so long from him. He minds that she thinks she can't ask for help, that maybe its because no one's helped her this whole time, and he feels like he can't breathe again like he's going to start drowning –

"It's not…it's my problem."

"Your problem is my problem," he says, "that's how we got into this situation, and that's how it's going to be."

"Ichigo," she protests.

"Do you sleep better, yes or no?"

She grumbles, the flush high on her cheeks, blooming around her ears. He tries not to feel smug, or glad that he's helping her – that he's making her life better. After all, she's done for him it's the very least he can do, and he tells her so.

"That's not…"

"True? I think you need to get some more rest, I'm sure you'll come up with a better argument," he retorts, and she scowls.

"Fine, then I will," and he isn't surprised when she climbs into his bed, only that she's lying there and looking up at him expectantly.

"Well?"

"Uh…"

"You said I need to sleep, so."

"So," he trails, trying to ignore the way his cheeks are the ones burning now.

With a roll of her eyes, she says his name impatiently, and he clears his throat to echo, "Right…right…"

Sleeping with Rukia, he finds, is actually a pretty easy thing to do, once she'd huffily told him to stop being so stiff and "_get with the hugging already, we both know you do it"_, he'd had little choice in the matter.

"You know, I've never actually…slept with you."

"Not without consent my consent you haven't."

He snorts an 'obviously', pinching her side, and she retaliates by squirming into him which _she really shouldn't be doing; he's a seventeen-year-old boy for god's sake_.

But – besides that – it's…nice.

Ichigo doesn't have to keep checking on her to make sure she's sleeping, he doesn't have to keep a hand on her as a physical anchor – he's got his arm around her waist for that, and every flutter of breath she expels and takes in, he can feel against his chest, and he mimics it until the pressure in his lungs dissipate.

They're spooned together, facing the wall, and while Ichigo had mentally told himself it would only be until she falls asleep – and he'd just drag the futon out of the closet to sleep on the floor – he succumbs to slumber without any effort.

It becomes something they do now.

She doesn't sleep as often at lunch as a result, and hardly ever when she's waiting for him after school which he counts as a plus.

She still goes out in the night to do her patrols without him; the night after they shared a bed, he'd waited in obvious tense silence for what she'd do next after coming through the window that Rukia snorted and told him, "Stop making that face, I'm coming."

After that, he'd gotten so used to her climbing into bed that he automatically just rolls over, throws an arm over her and goes back to sleep.

There's only one real moment he's aware of when she really questions it, though not enough for her to do anything about it when he'd grumpily squinted up at her before saying, "Are you coming to bed or not?"

Suffice to say, it's no longer something they talk or even think about really; it's as automatic and natural as everything is when it involves her.

He doesn't dream of drowning anymore, and if he does, he only has to see her lying beside him, blinking wide blue eyes at him, to breath deep and exhale.


End file.
